Assembly line apparatus



June 26, 1952 G. A. RUDOLFI 3,040,675

ASSEMBLY LINE APPARATUS Filed Feb. 25. 1957 5 Sheets-Sheet 1 June 26,1962 G. A. RUDOLFI 3,040,675

ASSEMBLY LINE APPARATUS v Filed Feb. 25. 1957 5 Sheets-Sheet 2 HMM June26, 1962 i G. A. RuDoLFl 3,040,675

ASSEMBLY LINE APPARATUS Filed Feb. 25. 1957 5 Sheets-Sheet 5 June 26,1962 G. A. RUDOLF! ASSEMBLY LINE APPARATUS 5 sheds-sheet 4 Filed Feb.25. 1957 June 26, 1962 G. A. RuDoLr-I 3,040,675

ASSEMBLY LINE APPARATUS Filed Feb. 25. 1957 5 sheets-sheet 5 tats arentIl c t 3,040,675 ASSEMBLY LiNE APPARATUS Gino A. Rndolfi, 7Stl1 AniseAve., Los Angeles, Calif.

'Filed Feb. 25, 1957, Ser. No. 642,675 f 6 Claims. (Cl. lim- 118) Thisinvention relates to an assembly-line structure for use by seatedworkers for the progressive assembly of work pieces.

A prevalent type of assembly structure comprises a long workbench for arow of workers seated on relatively high stools. The work pieces thatare moved from worker to worker along the workbench either rest on thetop surface of the workbench or are mounted on carriages that rolllalong the top surface of the bench. A high rack structure extendingupward from the floor adjacent the workbench on the side opposite fromthe seated workers provides tiers of inclined trays or baskets holdingcomponents to be assembled to the work pieces. Instruction sheets forguidance in the assembly procedure are customarily either mounted on therack structure or positioned face up in the inclined trays. assemblyline structure has numerous disadvantages.

Several of these disadvantages have a serious cumulative fatigue effect.The bench top is at a relatively high level requiring relatively highstools and, since the stools Such a prior art are so high it isnecessary to incorporate Afoot rests in the v bench construction. Suchan arrangement is not conducive to comfort for the workers and inducesunnecessary fatigue. Another fatigue factor is that the elevated benchtop requires the seated workers to work with their hands at relativelyhigh levels, the forearms of the workers normally extending upward asmuch as 45 degrees or more. A third fatigue factor is that the positionof the workbench relative to the seated Workers -tends to cause theworkers to hunch over the work pieces, and this j factor is aggravatedtoo often by the failure of the workers to move their stoolssuiiiciently close to the Work- Abench. Another factor contributing tofatigue is the necessity for the workers to `lean forward repeatedly toreach for components in the trays on the opposite side of the bench. Itis also necessary lfor the Workers to lean over in the same manner toread the instruction sheets.

Another disadvantage of the described prior art structure is that thetop of the bench is the only convenient place for miscellaneous items.It is natural for workers to lay tools and assembly components on thebench top and occasionally the workers also place the instruction sheetson the bench top. Consequently, it is normal for the bench top to be indisarray with a consequent unfavorable psychological effect on theworkers. If a soldering iron is used in an assembly operation, it iscommonly placed on the bench top where it becomes a hazard. Whenever itis necessary to shift a work piece from station to station by moving acarriage along the bench top, time is lost in moving these variousobstacles to clear a path for the carriage.

Another disadvantage is that confusion may arise as to the relation ofthe instruction sheets to the different assembly runs. Reference by aworker to the wrong instruction sheet -may cause serious and expensiveerrors.

lt has lbeen further found that there is a psychological handicap on.the part of the workers in facing the high rack structure across Atheworkbench. The workers have a sense of being hemmed in which increasesthe monotony of the work.

A still further disadvantage of the described assembly line structure isthat it requires a relatively large amount of valuable floor space perworker.

The present invention provid an assembly line construction that avoidsall of these disadvantages. The

2 workers are seated in comfortable chairs of convenient heightpermitting their feet to rest flat on the floor. Instead of a relativelyhigh workbench extending along the assembly line, a relatively low basestructure runs longitudinally of the assembly line and is provided withtrack means for conveying work pieces. Carriages on the track meansextend upward and outward from the base structure to hold the workpieces in positions for optimum comfort of the workers and optimumefficiency in the assembly operations. In the preferred practice of theinvention, the top of the base structure is approximately at the levelof the knees or the laps of the seated workers and the work pieces areheld in positions immediately above the workers laps. There is notendency for the workers to sit away `from their work and the workers'ture from the seated workers, special component racks are positionedbetween successive workers in the row of workers. Thus, each worker mayreach to one side 'for component parts without any necessity of changein body posture. component racks are releasably mounted on the basestructure itself leaving the oor space clear under the component racks.

A special feature of the invention is the concept of including trucks tomove the component racks bodily from the assembly lline to a supply roomwhere the racks are stocked with component parts. 'Ilhe usual procedureis to deliver the component parts to the assembly line in bags, trays orother containers for distribution to the trays in the upright rackstructure. The new procedure provided by the invention makes it possibleto distribute the parts directly to the racks at the point of supply,the parts being arranged on each component racks in an order convenientfor the worker that is to carry out the corresponding assemblyoperation. An important advantage of this arrangement is that while oneset of the component racks is in use at the assembly line structure foran assembly run, a second set of racks may be in the process of beingstocked in the supply room in preparation for a succeeding assembly run.

With the base structure at approximately 'lap height and withelimination of the necessity for a high bank of trays facing the seatedWorkers, the workers do not feel` hemmed in but rather are given a senseof spaciousness.

Preferably, there are two rows of workers facing each other across thelow base structure with two corresponding tracks for carriages and withcomponent racks on both sides of the base structure. The fact that therows of workers face each other lessens the tendency for the assemblyoperations to become monotonous.

A special feature of the preferred practice of the invention is themaximum convenience afforded the seated workers with respect to spacefor tools and miscellaneous objects. One provision in this respectycomprises a pair of lockers in the base structure at each assemblystation, a lefthand locker for use by a worker of one shift and arighthand locker for a worker of another shift. These lockers areprovided with doors which may be swung open to make the inner sides ofthe doors accessible to The work pieces are relatively -low In thepreferred practice of the invention, the' are mounted on the sides ofthebase structure. Inasmuch as it is more convenient to return tools to therack on the locker door and to place miscellaneous objects on thecomponent rack, the new structure induces'an orderly appearance alongthe assembly line with a favorable effect on the workers.

An important feature of the preferredV practice of the invention is theprovision of special holders for soldering irons that may be detachablymounted on the base structure. As will be explained, the holders providefor conv venient storageof the soldering irons and completely eliminatethe possibility of the workers being accidentally burned by thesoldering irons.v

The placing of the component racks in a row with the seated Workersresults in a substantial reduction in floor space; The saving in iioorlspace per worker if only one Vrow of workers is employed amounts toapproximately 1/3. If two rows of workers are employed on voppositesides of the assembly base structure, there is an additional reductionof 25 percent in the iloor space per worker. Thus, the combinedreduction in floor space per worker may amount to approximately 50percent.

y The assembly line structure of the invention is highly ilexible in anumber of respects. For example, the base structure is wiredy to permitvarious devices to be plugged in at will, including soldering irons andbuzzer test circuits. Further ilexibility in another sense is providedby making the assembly line structure in short units that may bepositioned end to end to form a composite assembly line structure of anydesired length. Where several such composite assembly line structuresare used, they may be individually varied in length to meet changingproduction requirements. The assembly line structure is further ilexiblein that the carriages for the work pieces may be added or removed at anypoint. Thus, carriages may be removed at one station'along an assemblyline where the assembly of one run of work pieces is completed andcarriages may be added at the next station for the initiation ofanother-run. Y t

The various features and advantages of the invention may be understoodfrom the following detailed description, considered with theaccompanying drawings.

In the drawings which are to be regarded as merely illustrative: Y

FIGURE l is a perspective view of the presentlyprekferred,embodirnent'of the assembly line structure;

Y FIGURE 2 is a perspective view on an enlarged scale of one of thecomponent racks of the assembly line struc- Y ture; f

showing how a component rack is supportal by an arm that is releasablymounted ture; K p Y 1 FIGURES 5 and 6 are simplified sectional viewsshowin a socket in the base strucing two stages in the movement of thesupport arm'of theV component rack into a 'mounting socket; v

FIGURE 7 is a view similar to FIGURES 5 and 6,

on a somewhat larger scale showing the ,support arm of the componentrack in its mounted position i-n a socket;

FIGURE 8 is a perspective view of a soldering iron holder that isprovided by the invention;

FIGURE 9 is a longitudinal section of the soldering iron holder taken asindicated by the line 9 9 of FIG- URE 8;

FIGURE l0 is a perspective view, partly broken away, showing a carriagemounted on a track for movement of work pieces along the assembly line;

`assembly line procedure since the tracks for the carriages mounted onthe component v FIGURE 11 is a transverse sectional view of the trackshowing the carriage in its normal engagement therewith;

FIGURE l2 is a Viewv similar to FIGURE ll showing how the carriage maybe disengaged from the track; and

FIGURE 13 is a perspective view from below showing how the support armof a panel for instruction sheets may be releasably mounted on thecarriage.

FIGURE l shows one unit or section of an assembly line structure, whichis generally designated by numeral 20, and which may be combined withother similar units positioned end to end to form a composite assemblyline structure of any desired length. Thus, a second assembly linestructure unit 20a: shown in phantom abuts one end of the unit 20.

The assembly line structure unit 20 is intended for use with two rows ofseated workers and is of a length to provide two work stations oneachside of the structure. Each of the four work stations of the unit isprovided with a comfortable chair 22 of conventional height to seat aworker. Only Aone of the four chairs is shown in the drawing, the restbeing omitted for sake of clarity of illustration.

The base structure of the unit includes a pair of spaced pedestals orstanchions 24 and a top assembly supported thereby. In the constructionshown, the top assembly comprises atop plate 25 and a lower plate 26interconnected by transverse members 28 to form a double wall.

An electric conduit 30 in this top assembly supplies current to pairs ofelectrical outlets 32 into which various electrical devices may beplugged, such as soldering irons and buzzer test devices. In theconstruction shown, there are three pairs of the jacks 32 on each sideof the support structure.

The top plate 25 and the lower plate 26 of the top assembly areadditionally interconnected by a metal track member 34 on each side ofthe base structure. The two track members 34 are special channel membersand serve as structural beams of the base structure. Each end of each ofthe two track'rnembers 34 is provided with a U-shaped bracket 35 so thatshort guide bars 36 may be inserted in the brackets at the adjacent endsof the abutting assembly line structure units to hold the units inaccurate longitudinal alignment with each other.

At each vof the four sta-tions where a chair 22 is provided to seat aworker, there is a clear space for ample leg room under the topVassembly and there are two lockers 38 and 40 on opposite sides of thisclear space for use by workers of two dierent shifts. The lefthandlocker 38 at each station has a door 42 that opens to the left and therighthand locker 40 has a door 44 that opens to the right, both doorsOpening in a direction away from the worker seated at the station. Asshown in FIGURE l, each of these doors 42 and 44 is provided on itsinner side with a suitable tool rack 4S to hold a set of tools. When alocker door is in open position, the tool rack 45 on'the inner sidethereof is within convenient reach of the seated worker.

As heretofore indicated, the assembly line structure includes a numberofV component racks, each generally designated by numeral 46, which arepositioned between successive workers in a row of the seated workers.These component racks 46 may either stand on the floor or be supportedby the base structure. A feature of this particular embodiment of theinvention is that the component racks 46 are detachably supported by thebase structure.

Preferably, as best shown in FIGURE 2, each of the component racks 46comprises an upright metal frame 48 and a horizontal metal frame i),that extends in opposite directions from the lower edge of the uprightframe. There are two spaced rows of cross rods 52 on the opposite sides,respectively, of the upright frame 48 to receive receptacles 54 of awell known type for holding supplies of assembly components. Thisarrangement permits receptacles 54 to -be arranged on the opposite sidesof the upright frame 48 for use, respectively, by the seated workers atthe two adjacent stations. As best shown in FIGURE 3, each of thereceptacles 54 has a downwardly extending back tongue 55 for supportingengagement with a pair of the cross rods 52 to permit the receptacle tobe releasably mounted on the upright frame 4S.

The horizontal frame 5i? of .the component rack has spaced cross rods 56from which various objects may be suspended, if desired, such as acomponent S8 `shown in FIGURE 1. The horizontal frame 50 is alsoprovided with low guard rails 66 at its opposite ends to keep objectsfrom rolling oft the frame.

In the preferred practice of the invention, shelf panels 62 are providedfor use on the bottom frame 56 of the component rack 46 on oppositesides of the upright frame Each of these removable shelf panels 62comprises a piece of sheet metal formed with downwardly extending endflanges 64 to engage the opposite ends of the metal frame 50 and formedwith an upright ilange 65 for abutment against the inner side or thecorresponding guard rail 60 to keep the shelf panel securely inposition. The addition of a shelf panel 62, when desired, provides aconvenient space for small objects as may be seen in FIGURE 1.

Each of the component racks 46 may be adapted in any suitable manner fordetachable mounting on the base structure. In this instance, each of thecomponent racks t6 is united with a cantilever support arm 66 that has atongue 68 at its end for insertion into a complementary socket 76 in theside of the base structure.

As best shown in FIGURE 4, each of the sockets 70 may be formed byattaching a U-shaped bracket 72 of appropriate dimensions to the underside of one of the track members 34, the track member forming the upperwall of the socket and the bracket forming the side and bottom walls. Inthe construction shown, the U-shaped bracket 72 has a downwardlyextending front webb 7 d on the back of which is mounted an electricaloutlet box 75l to provide one of the previously mentioned pairs of jacks32. Preferably, the socket 7n provides greater vertical clearance thanthe thickness of the tongue 63 so that the inserted tongue takes aninclined position as shown in FIGURE 7. The tongue is correspondinglyinclined relative to the support arm 66 to hold the support armsubstantially horizontal.

Preferably, means is provided to lock the tongue 68 against withdrawalfrom the socket 70. For this purpose, the tongue 68 may be provided witha downwardly extending lug 76 to seat in a corresponding recess in theform of an aperture 7S in the bottom wall of the socket 7i. Obviously,the lug may be carried by the socket instead of the tongue, with thetongue recessed to receiv the lug.

The described arrangement makes it a simple matter to mount or dismounta component rack 46 in a rapid manner. Thus, FIGURES 5 and 6 show howthe tongue 68 may be inserted into the socket 7d with the trailing endof the tongue inclined upward to permit the lug 76 to enter the socket.Once the lug 76 is linside the socket, the support arm 66 may be loweredto position the various parts relative to each other as shown in FIGURE7.

FIGURE l shows a hand truck 8i) that may be used to convey a number ofthe racks 46 to and from a supply room where the component racks may bestocked with assembly parts. Preferably, the assembly parts are arrangedon the rack in whatever sequence is to be followed at the particularassembly station and the upright frame its of the rack makes itconvenient to place the receptacles 5'4 in any desired arrangement forthis purpose.

The preferred practice of the invention further includes soldering ironholders 82 which may be constructed as best shown in FIGURES 8 and 9.The holder 82 is designed for a conventional soldering iron having ahandle 84, a handle guard 85 and a shank S6 that incorporates a heatingelement .to heat the usual copper tip 8S. An electric cord 9i? forenergizing the soldering iron extends through the handle 84 andterminates in a jack plug 92 to tit into any one of the previouslymentioned jacks 32 onthe base structure.

The holder 82, which preferably is slightly inclined downward, has aninner metal tube 94 to receive the shank 86 of the 4soldering iron andhas. a substantially larger outer guard tube 95 that is formed withnumerous perforations 96. The outer guard tube 95 is connected to theinner tube 94 solely by an annular end wall 98 at the lower end of theholder. Both ends of the inner metal tube 9d arer open and the free endMtl of the tube terminates short of the corresponding end of the outerguard tube 95. In the construction shown, this corresponding end of theouter guard tube 94 has an inclined disc 162 united therewith and thisdisc has a central aperture 104 to receive the soldering iron 'shank 86.The inclination` of the disc 102 causes the disc to make contact withonly one point of the handle guard 85 when the soldering iron isinserted into the holder. v

The soldering iron holder may be mounted permanently on the assemblyline base structure or may be adapted for such mounting in any suitablemanner. In the constructions shown, a support arm 10S in the form of anupright metal plate is rigidly united with the outer tube 95. This plateis provided at its lower end with a leaf spring bracket 1% by means ofwhich the soldering iron holder may be removably mounted, for example,on a cantilever support arm 66 of a component rack 46. Preferably, thesupport arm 105 is provided with a brush 108 having metal bristles forthe convenience of the worker in cleaning the tip of the soldering iron.

The described construction of the soldering iron holder 82 keeps theouter guard tube 95 relatively cool. In fact, the guard tube may begrasped yby the hand without undue discomfort even when -the solderingiron has been stored in the holder for several hours at maximumtemperature.

A number of factors account for the relatively low temperature of theguard tube 95, Thus, the inner tube 9d that is directly heated by thesoldering iron is cooled by radiation through the perforations 96 of theouter tube as Well as by convection. Preferably, cool air enters theperforations 96 on the under side of the holder and the heated air ilowsout of the perforations on the upper side of lthe guard tube. The factthat the soldering iron holder is nearly horizontal is important, theupwardly traveling heated air flowing away from the outer guard tube 95instead of along the guard tube. The remaining heatof the inner tube 94is conducted by the annular end wall 9S to the outer guard tube 95 butits residual heat is of low magnitude and is rapidly dissipated by theguard tube. Since the inclined disclZ of the holder makes only pointcontact with the handle guard 85 of the soldering iron and since thefree end lltll of the inner tube 94 is spaced from this inclined disc,all the heat that travels by conduction from the inserted soldering ironto the outer guard tube 95 must follow the relatively Along path to thefixed end of the inner tube at the annular end wall 92.

As best shown in FIGURE l0, each of the track member 34 has alongitudinal bottom web llt), an upright web M2 along its innerlongitudinal side, and an overhanging longitudinal web 114 that is acontinuation of the upright web. Either the bottom web il@ which is onerail element of the track or the overhanging web 114 is anged to retaincarriages on the track. In the 'Z construction shown, the bottom web11i? is formed with a relatively low upright flange 11S along theouterlongitudinal side ofthe track member.

FIGURES 1G, l1 and l2 show how a suitable carriage, generally designatedby theY letter C, is constructed for releasable engagement with a trackmember 34. The carriage C has a base plate V116 that is stirened by adownwardly extending ange 118 along one Vside and an upwardly extendingflange 1253 along the other side. As indicated in FIGURE 1l, two axles124 and 125 at each end or' the carriage are bonded to each other bywelding 126 and are bonded to the under side of the base plate 116 byweldingY 123. The two lower axles 124 journal corresponding wheels 130at the outer edge of the base plate 116 to ride on the lower railelement 11d of the track member, and the two upper axles 125 journalwheels 132 at the inner edge of the base plate to ride on the undersideVof the overhanging rail element 114.

Each carriage C further includes a tubular member or pedestal 13d thatis united with the base plate 116 centrally thereof and extends upwardlyfrom the base plate in an outwardly inclined direction. The upper end ofthis tubular member ldis suitably adapted to hold work piecesforconveyance along the track member. For this purpose the upper end ofthetubular member 134 may be provided with a horizontal disc 135 tocarry a well known device commonly termed a power4 arm. Such a power armhas a socket member 136 which may be ilxedly attached to the horizontaldisc 135 by suitable screws 138.

The socket member 136 forms a socket 1411 having a vertical slot 142,the socket Vengaging a ball element 144 at the end of a support arm 14Swith the support arm extending through the slot. A short handle 146 maybe operated to tighten or release the ball element 144 in the socket.The outer end of the support arm carries ra support plate 14g (FGURE l)which has numerous apertures 1S@ therein to receive screws or bolts bymeans of which work pieces may be mounted on the supportl arm forassembly operations.

In the preferred practice ofv the invention, a panel 152 for aninstruction sheet is carried by the carriage C in a position facing the'worker from across the work piece. ln the construction shown, the panel152 is made of Vsheet metal and is provided with flanges 154 on thesides and bottom to retain anV instruction sheet. The panel 152 iscarried'by an angular support arm 155 which is detachably mounted on thecarriage C in a suitable manner. For this purpose, the undersideV of thecarriage disc 135 may be provided with a U-shaped bracket 156, as shownin FGURE 13. The bracket o has a slot 158 to receive a downwardlyextending stud 160 carried by the support arm 155. When the end of thesupport arm 15S is fully inserted into the socket formed by the bracket156, the stud 169 extends through the slot 15S and a wing nut 162 may betightened on the stud 169 to secure the support arm lin a releasablemanner.

it may be readily appreciated by reference to FIGURE ll that with thecarriage structure extending upward and outward from the track member 34towards the seated worker, the center of gravity ofthe carriage togetherwith a work piece thereon is positioned outward from the track member sothat the carriage tends to tilt about the near wheels 130 as a fulcrumin a manner that presses the near wheels downward against the bottomrail element 11b and presses the far wheels 132 upward against theoverhanging rail element 114. As a result, the carriage rides along therack member .in a highly stable manner.

FGURE l2 shows how a carriage may be easily and quickly disengaged fromthe track member 34. The

carriage is rst swung upward sufficiently to lift the two near wheels130 above the track flange 115 and then the carriage is shifted outwardto the position shown in solid lines in FIGURE 12 where the near wheels13G are out- Clt 8 side the flange 15. The carriage is then swung backto its normal angle and shifted outward still further to the positionshown in broken lines in FIGURE 12 where the far wheels 32 are clear ofthe overhang-ing rail element 114. The carriage may then be lifted fromthe track member. rlhe reverse procedure is followed to place a carriagein running engagement with the track member. Thus, a carriage may beengaged with or disengaged frorn a track member 34 at any intermediatepoint of the track member.

My description in specific detail of the selected ernbodiment of theinvention will suggest to those skilled in the art various changes,substitutions and other departures 4from my disclosure within the spiritand scope of the appended claims.

l claim:

l. in an assembly line construction for the progressive fabrication ofwork pieces by a row of seated workers, the combination of a basestructure having a rst support portion extending along the assembly lineconstruction in the direction of the row of seated workers, the basestructure alsohaving rst and second side portions extending from thesupport portion at opposite lateral extremities of the support portion,the extent of the rst side portion along the first support portion beingless than the extent of the second side portion along the first supportportion, the base structure further having a second support portionextending partially from the second side portion toward the rst sideportion in a direction having a major component parallel to the tirstsupport portion, and a carriage movable along the base structure in 4thedirection of the row of seated workers, the carriage including a iirstwheel rotatable on the trst support portion at a position near the firstside portion and including a second wheel rotatable-on the secondsupport portion at a-position near the second side portion, the carriagealso including means coupling the irst and second wheels to the carriagefor respective rotation on the iirst and second support portions of thebase structure.

2. The combination set forth in claim l in which a pedestal is includedin the carriage and is disposed in a direction extending away from thefirst support portion of the base structure at an'inclination to the rstand second portions of the base structure to facilitate the dispositionof the rst wheel against the rst portion and the disposition of thesecond wheel against 'the second support portion of the base structureand in which means are included on the pedestal to hold the work pieces.

, 3. In an assembly line construction for the progressive fabrication ofWork pieces by a row of seated workers, the combination of a. basestructure extending along the row of workers and having a supportportion, the base structure having a ange portion extending from thesupport portionat a first lateral side of the support portion, the basestructure having a side portion extending from the support portion at asecond lateral side of the support portion opposite to the rst lateralside and extending in substantially the same direction as the liangeportion and through a distance greater than that of the iiange portion,the base structure having a second support portion extending from theside portion at a position removed from the rst support portion andextending in a direction appreaching the flange portion, and a carriagemovable on the base structure along the row of Workers, the carriageincluding a rst pair of wheels displaced from each other along the rowof workers and movable on the iirst support portion at a lateralposition adjacent to the ilange portion of the base structure andfurther including a second pair of wheels displaced from each otheralong YVthe row of workers and movable on the second support portion ofthe base structure at a lateral position adjacent to the side portion ofthe base structure, the carriage further including axlemeans forsupporting the iirst and second pairs of wheels to obtain a rotarymovement of the rst pair of Wheels on the iirst support portion of thebase structure and a rotary movement of the second pair of wheels on thesecond support portion of the base structure, the carriage furtherincluding means for obtaining a tilt of the carriage in a direction todispose the iirst pair of Wheels against the rst support portion of thebase structure and to dispose the second pair of wheels against thesecond support portion of the base structure.

4. In an assembly line construction for the progressive fabrication ofwork pieces by a row of seated workers, the combination of a basestructure having a tirst support portion extending along the basestructur. in the direction of the row of Workers, the base structurehaving a ange portion extending for a -limited distance from the iirstsupport portion at a iirst lateral side of the support portion, the basestructure having a side portion extending from the support portion at asecond lateral side opposite to the rst lateral side, the base structurehaving a second support portion extending for a limited distancey fromthe side portion in a direction having a major cornponent parallel tothe iirst support portion and approaching the ange portion, the secondsupport portion extending for a distance to dene an opening between theange portion and the second support portion, a carriage movable alongthe base structure in the direction of the row of workers, the carriageincluding a iirst pair of Wheels disposed in the direction of theworkers at the rst lateral side of the support portion and including asecond pair of Wheels disposed in the direction of the Workers at thesecond lateral side of the support portion, the second pair of wheelshaving a diameter slightly less than the distance l'between the iirstand second support portions of the base structure, the carriage furtherin cluding axle means for respectively supporting the irst and secondpairs of wheels on the first and secondV support portions of the basestructure, the carriage further including means for applying a torque toone of the pair of wheels with the other pair lof Wheels as a pivot tomaintain the first pair vof wheels on the tirst support portion of thebase structure and to maintain the second pair and to x the supportplate relative to the pedestal in anyV pivotal position.

6. The combination set forth in claim 5 in which a panel is attached tothe pedestal Ito carry instruction sheets for the seated workers.

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